Beyond the Standard Model Higgsat ATLAS

Hal Evans, Indiana University, for the ATLAS Collaboration

Mitchell Workshop on Collider & Dark Matter PhyiscsMitchell Institute for Fundamental Physics

Texas A&M University12 – 15 May, 2014

H. Evans Mitchell Workshop - May 12, 2014 2

The Higgs We FoundThe Higgs We Found

Signal Strength: μ = (σ×BR)/(σ×BR)SM Spin Structure (vs 0+)

verySM-like

verySM-like

but still roomfor

somethingnew

ATLAS-CONF-2014-009Phys Lett B 726 (2013) 120

H. Evans Mitchell Workshop - May 12, 2014 3

Beyond the SMBeyond the SM

Large number of possible models ==> two strategies− consider only simplest extensions of the SM− topology-driven (~model independent) searches

Models considered− Minimal Composite Higgs Model (MCHM)

> Higgs = pseudo-Nambu-Goldstone boson ==> explains scalar naturalness

− Single additional electroweak singlet> simplest extension, two CP-even Higgs bosons

− Two Higgs Doublet Models (2HDM)> additional doublet ==> h0, H0 (CP-even), A0 (CP-odd), H± ==> resolves hierarchy problem> 4 types based on coupling structure (Type-II = MSSM)

− Higgs Triplets> h0, H0 (CP-even), A0 (CP-odd), H±, H±± ==> explains neutrino masses/mixings

− Next-to-Minimal SUSY (NMSSM)> MSSM + complex singlet(S): generates MSSM μ-term through S spontaneous symmetry breaking

− Higgs and Dark Matter> Dark Matter couples primarily to the Higgs ==> “invisible” decays

H. Evans Mitchell Workshop - May 12, 2014 4

ATLAS BSM Higgs AnalysesATLAS BSM Higgs Analyses

Published− “Search for top quark decays t→ qH with H→γγ using the ATLAS detector”, arXiv:1403.6293, submitted to JHEP− “Search for Invisible Decays of a Higgs Boson Produced in Association with a Z Boson in ATLAS”, arXiv:1402.3244,

accepted by PRL− “Search for a Multi-Higgs Boson Cascade in W+W- bbar events with the ATLAS detector in pp collisions at √s = 8 TeV”,

Phys. Rev. D 89, 032002 (2014), arXiv:1312.1956− “Search for a light charged Higgs boson in the decay channel H+ → csbar in ttbar events using pp collisions at √s = 7

TeV with the ATLAS detector”, Eur. Phys. J. C, 73 6 (2013) 2465, arXiv:1302.3694− “Search for charged Higgs bosons through the violation of lepton universality in ttbar events using pp collision data at

√s = 7 TeV with the ATLAS experiment”, JHEP03(2013)076, arXiv:1212.3572− “Search for the neutral Higgs bosons of the Minimal Supersymmetric Standard Model in pp collisions at √s =7 TeV with

the ATLAS detector”, JHEP02(2013)095, arXiv:1211.6956− “Search for doubly-charged Higgs bosons in like-sign dilepton final states at sqrt(s) = 7 TeV with the ATLAS detector”,

Eur.Phys.J. C72 (2012) 2244, arXiv:1210.5070

Preliminary− “Constraints on New Phenomena via Higgs Coupling Measurements with the ATLAS Detector”, ATLAS-CONF-2014-010− “Search for Higgs bosons in Two-Higgs-Doublet models in the H → WW → eνμν channel with the ATLAS detector “,

ATLAS-CONF-2013-027− “Search for a Higgs boson decaying to four photons through light CP-odd scalar coupling using 4.9 fb-1 of 7 TeV pp

collision data taken with ATLAS detector at the LHC”, ATLAS-CONF-2012-079

+ other, superseded results (not discussed here)− see: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResults

2HDM Triplet NMSSM Dark MatterSingletMCHM

H. Evans Mitchell Workshop - May 12, 2014 5

ATLAS DetectorATLAS Detector

2012 ATLAS Detector

2012 Trigger/DAQ

Rate (kHz) 2012 2015

Bunch Crossing 20,000 40,000

L1 Trigger 75 100

to disk 0.4 ~1

H. Evans Mitchell Workshop - May 12, 2014 6

Data Taking (pp Mode)Data Taking (pp Mode)

Year √s BC Delivered Good Qual

2010 7 TeV 50 ns 0.048 fb-1 0.045 fb-1

2011 7 TeV 50 ns 5.46 fb-1 4.5 fb-1

2012 8 TeV 50 ns 22.8 fb-1 20.3 fb-1

2015 13 TeV 25 ns ~40 fb-1

pileup

H. Evans Mitchell Workshop - May 12, 2014 7

General BSM Higgs Search FeaturesGeneral BSM Higgs Search Features

Triggers

Physics Objects

Pileup− important effect for jets, taus,

missing ET, b-tagging

− less of an issue for e/μ

2012 Trigger Level-1 Threshold [GeV] “Analysis” Threshold [GeV]

single e 18 (isol) / 30 (non-isol) 25 / 40

di-photon 2 x 10 (isol) 2 x 15

single μ 15 20

tau+ETmiss 15, 35 40, 60

e / γ calorimeter, tracking, γ→e+e-

μ muon system, tracking

tau BDT: collimation, isol, shower profile

jets anti-Kt (R=0.4)

ETmiss objects + topo clusters in calo

b-jets lifetime-related Neural Net

Z / W Z → ℓℓ / W → ℓν, qq'

top t → b W

H. Evans Mitchell Workshop - May 12, 2014 8

Minimal Composite Higgs Model&

Additional EW Singlets

Minimal Composite Higgs Model&

Additional EW Singlets

H. Evans Mitchell Workshop - May 12, 2014 9

MCHM & Additional Singlet ResultsMCHM & Additional Singlet Results

Re-analysis of all ATLAS Higgs coupling measurements− h→γγ, h→ZZ*, h→WW*, h→ττ, h→bb

Minimal Composite Higgs Modelscouplings to Vector Bosons & Fermions modifiedfrom SM values:

Additional EW Singleth & H couple with reduced strength

κV ,κH=F(ξ=v2 / f2)

95% CL f [GeV]

MCHM4 >710(460)

MCHM5 >640(550)

σh=κ2σh,SM σH=κ ' 2

σH ,SM

BRh, i=BRh ,SM, i BRH, i=(1−BRH ,new )BRH ,SM, i

κ'2 < 0.12(0.29)

ATLAS-CONF-2014-010

(κ' 2)

ATLAS-CONF-2014-009

H. Evans Mitchell Workshop - May 12, 2014 10

Two Higgs Doublet ModelsTwo Higgs Doublet Models

H. Evans Mitchell Workshop - May 12, 2014 11

2HDM Features2HDM Features

General Features− 5 physical Higgs particles: h0, H0 (CP-even), A0 (CP-odd), H±

− separate vev's for each doublet: v12 + v2

2 = (246 GeV)2 tanβ = v2 / v1

− 5 parameters: mh , mH , mA , mH± , tanβ, α (h0–H0 mixing)

4 Types suppress FCNCs

Coupling Scale Type I Type II Type III Type IV

doublet 1 vector bosons u-type q's q's as type I q's as type II

doublet 2 fermions d-type q's ℓ's as type II ℓ's as type I

κV sin(β−α) sin(β−α) sin(β−α) sin(β−α)

κu cos α / sin β cos α / sin β cos α / sin β cos α / sin β

κd cos α / sin β −sin α / cos β cos α / sin β −sin α / cos β

κℓ cos α / sin β −sin α / cos β −sin α / cos β cos α / sin β

MSSM

h0 co

uplin

gs /

SM

H. Evans Mitchell Workshop - May 12, 2014 12

2HDM Coupling Limits2HDM Coupling Limits

From ATLAS SM Higgs coupling measurements− h→γγ, h→ZZ*, h→WW*, h→ττ, h→bb

ATLAS-CONF-2014-010

ATLAS-CONF-2014-009

Type I Type II Type III Type IV

SimplifiedMSSM

Consistent w/ SM-like alignment: cos(β−α)~0 − observed limits better than expected b/c meas. couplings generally > SM

H. Evans Mitchell Workshop - May 12, 2014 13

2HDMs and Vector Bosons2HDMs and Vector Bosons

Search for Heavy Higgs: H0 → WW → ev μv− selection as in SM h0 → WW analysis

> e + μ + Etmiss + 0 or 2(non-b) jets

− Neural Net to distinguish signalfrom background (mainly di-boson)

ATLAS-CONF-2013-027

Type I Type II

H. Evans Mitchell Workshop - May 12, 2014 14

2HDMs and Fermions2HDMs and Fermions

Higgs coupling to τ-leptons and b-quarks enhanced (large tanβ)− associated production with b-quarks (h/H/A b) increasingly important− decays h/H/A → ττ, bb dominate

Charged Higgs production involves top quarks− decay mainly via: H+ → τv

> H+ → cs also possible

τ/b/t play an importantrole in many searches

mH+ < mt mH+ > mt

t → b H+ associated production

H. Evans Mitchell Workshop - May 12, 2014 15

Examples of τ & b-ID at ATLASExamples of τ & b-ID at ATLAS

b mis-tagging rate (εb = 70%)

τ→hadrons tagging: bgrd vs eff.

H. Evans Mitchell Workshop - May 12, 2014 16

h/H/A → ττ, μμ in MSSMh/H/A → ττ, μμ in MSSM

h/H/A (φ) production via: gg→φ and φb(b), then φ → ττ or μμ− BR(φ→ττ) ~ 10% in mass range, BR(φ→μμ) ~ 0.04% (clean signature)

> use τeτμ (6%), τeτhad (23%), τμτhad (23%), τhadτhad(42%)

− separate into events with and without b-jets

JHEP 02(2013)095

complementary exclusion to LEP generic scalar boson: gg-fusion & b-assoc.

H. Evans Mitchell Workshop - May 12, 2014 17

Charged Higgs SearchesCharged Higgs Searches

Indirect search: ℓ universality− compare BR(tt → e/μ/τ)

Direct (two jet) search: mH+<mt

− − search for a peak in M(cs)

> kinem. fit: jets↔partons

t t̄ → H+(c s̄)b W−

(e/μ ν)b

Rl =BR( t t̄ →bb̄+e/μ τhad+Nν)

BR( t t̄ →bb̄+eμ+Nν)

EPJ C73 6 (2013) 2465JHEP 03(2013)076JHEP06(2012)039

interpretation w/in MSSM − incl. τhad+jets MT

H. Evans Mitchell Workshop - May 12, 2014 18

Charged Higgs Searches (cont)Charged Higgs Searches (cont)

Direct search in the H+ → τ v mode− mH+ < mt:

− mH+ > mt:

− challenging all-hadronic mode

t t̄ → H+ ( τhad ν)b W (qq̄ ' b̄)b

gb̄ → t̄ (qq̄ ' b̄) H+ ( τhad ν)

gg → t̄ (qq̄ ' b̄)b H+ ( τhad ν)

mH+< mt

mH+> mt

interpretation w/in MSSM (mhmax scenario)

ATLAS-CONF-2013-090

H. Evans Mitchell Workshop - May 12, 2014 19

2HDM multi-Higgs Cascade2HDM multi-Higgs Cascade

Search for: H0 → WH+ → WWh0 → WWbb− same topology as top-pair events− distinguish using Boosted Decision Tree

> uses: mbb , mbbW , mbbWW , Δrbb , mtlep,,had, mt – mtbar

− trained at 36 different (mH0 , mH+) points

> mH0: 325–1025 GeV ; mH+: 225–925 GeV

expected limits (95% CL) observed limits (95% CL) limits on σgg→H0obs/σgg→H0

2HDM-II

PRD 89 (2014) 032002

upper limits still > theoretical (SM-like) H0 cross-section − but getting close in high-mass region

H. Evans Mitchell Workshop - May 12, 2014 20

2HDM Higgs & FCNC Top Decays2HDM Higgs & FCNC Top Decays

t → c h0 is GIM-suppressed in the SM (BR ~ 3∙10-15)− can reach ~0.15% in some 2HDM Type-III models

Search in− small h → γγ BR (0.23%) offset by distinctive signature

t t̄ → [h(γ γ)c /u] [W (e/μ ν ,q q̄ ')b]

arXiv:1403.6293√λ tcH2

+λ tuH2

< 0.17 (0.14 expected)

H. Evans Mitchell Workshop - May 12, 2014 21

Other BSM Higgs:Higgs Triplet Models &

Next-to-Minimal Supersymmetry

Other BSM Higgs:Higgs Triplet Models &

Next-to-Minimal Supersymmetry

H. Evans Mitchell Workshop - May 12, 2014 22

Further Beyond the SMFurther Beyond the SM

Higgs Triplet: H++ → ℓ+ℓ+

− same sign: ee, eμ, μμ eventsLight CP-odd Higgs in NMSSM

− h0 → aa → γγ γγ (ma < 3 mπ0)

− gg → a → μμ (ma < 2 mB)

HL++

HR++

EPJ C72 (2012) 2244

ATLAS-CONF-2012-079

ATLAS-CONF-2011-020

H. Evans Mitchell Workshop - May 12, 2014 23

Dark Matter and the HiggsDark Matter and the Higgs

H. Evans Mitchell Workshop - May 12, 2014 24

Higgs Portal to Dark MatterHiggs Portal to Dark Matter

WIMP Dark Matter candidate could interact mainly with Higgs− increase Z h0 → ℓℓ + Et

miss rate

− modify visible h0 decay rate: h → γγ, ZZ*(4ℓ), WW*(ℓvℓv), ττ, bb

ATLAS-CONF-2014-010arXiv:1402.3244

combine Zh → ℓℓ & SM coupling meas's

stringent constraintsat low χ mass

(but model-dependent)

H. Evans Mitchell Workshop - May 12, 2014 25

LHC's Future PlansLHC's Future Plans

√s = 13-14 TeV; L → 2×1034 cm-2 s-1; ∫L dt ~ 120 fb-1√s = 13-14 TeV; L → 2×1034 cm-2 s-1; ∫L dt ~ 120 fb-1

√s = 14 TeV; 5×1034 cm-2 s-1; 3,000 fb-1√s = 14 TeV; 5×1034 cm-2 s-1; 3,000 fb-1

√s = 14 TeV; 2×1034 cm-2 s-1; 350 fb-1√s = 14 TeV; 2×1034 cm-2 s-1; 350 fb-1

CERN update: Dec. 2, 2013

H. Evans Mitchell Workshop - May 12, 2014 26

ATLAS: Goals & ChallengesATLAS: Goals & Challenges

LHC upgrades ==> substantial challenges for ATLAS− trigger, data acquisition, tracking, data processing, ….

But also opportunities: energy, integrated luminosity− See talk by Carmen Garcia for more details

Phase Pileup Major ATLAS Changes

Run 1 (2012) 20

Run 2 (2015-18) 43 L1 topological trigger, Inner Pixel Layer

Run 3 (2020-22) 50-80 forward muon syst, readout/trigger

Run 4 (2025...) 140-200 new tracking, trigger architecture

CERN-2012-022

current h→γγ

ATL-PHYS-PUB-2013-015ATLAS-CONF-2014-010

SM Higgs Couplings

2HDMType IILimits

H. Evans Mitchell Workshop - May 12, 2014 27

ConclusionConclusion

Discovery of a Higgs boson has not stopped BSM searches− observed couplings limit many models though

Focus on simplest extensions of the SM & model-indep searches− emphasis on Two Higgs Doublet Models, but others explored as well− results rely on excellent performance of ATLAS detector

> e, μ, γ, τ- and b-tagging, Etmiss, top

− no evidence for Higgs beyond the SM found yet

Upgrades to LHC and ATLAS will broaden the search− higher mass reach & increased coupling sensitivity− but significant challenges for detector, trigger, analyses